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The “Drink Mixer” Reliability and Safety Analysis Criticality Levels • • • HIGH • Failure that causes system instability • Possible damage to user and/or system MEDIUM • Failure that affects audio processing • Affects operability of system LOW • LCD malfunction, inconvenience to user • No damage to device Component Analysis Failure Rates in the worst case scenario • ADSP-21262 Microcontroller • • ARM9 Microcontroller • • MTTF = 26.68 years ATMega32A Microcontroller • • MTTF = 5.73 years MTTF = 44.94 years 5V Linear Voltage Regulator • MTTF = 70.29 years Hammer ARM9 DSP LED Driver ATMega32A Power Supply FMECA Table 1 – Hammer ARM9 Failure No. 1A 1B 1C 1D 1E Failure Mode Possible Causes Micro remains in reset mode Reset switch is broken and stays in “pressed” state ATMELS and Hammer cannot communicate because Hammer cannot understand 5V logic Contrast is set either all the way up or all the way down LCD does not receive data I2C level shifter fried Failure Effects Microcontroller fails to run program, also cannot reprogram memory User interface seems to be working, but audio is not Erroneous/Sporadic ARM9 is fried data sent to the DSP Criticality Remarks Medium Medium criticality because it disables the functionality of the system Observation with DMM and Logic Analyzer Medium Medium criticality because it disables the functionality of the system Observation with DMM Low Low criticality because it is simply a nuisance to the user LCD will not Observation with change the display, Oscilloscope but the touch screen works Low Low criticality because it is simply a nuisance to the user Audio levels are sporadic. Possibly very high output levels. High High criticality because if levels are too high, they can be harmful when amplified Contrast voltage divider Cannot adjust the resistor is shorted contrast on LCD ZIF connector has bent pins or Hammer has burned out pins Method of Detection Observation with DMM Observation with Logic Analyzer FMECA Table 2 – DSP Failure Failure Mode No. 2A Micro remains in reset mode 2B Possible Causes Failure Effects Reset switch is broken Microcontroller and stays in “pressed” fails to run state program, also cannot reprogram memory Memory space is too SRAM chip burned Audio Processing small out is greatly lagging Method of Criticality Detection Observation with Medium DMM Remarks Medium criticality because it disables the functionality of the system Observation with Medium DMM and Logic Analyzer Medium criticality because it disables the essential functionality of the system 2C -If only one side: No power sent to individual LEDs - If both sides: SPI signal not present or sampled incorrectly -If only one side: LED Output amplitude driver is burned out LEDs are not - If both sides: SPI is lighting not working on DSP Observation with Low DMM and Logic Analyzer Low criticality because it is simply a nuisance to the user (Although it is one of our current PSSCs, so it is critical) 2D Erroneous/Sporadic output levels SHARC is fried Observation with High Logic Analyzer High criticality because if levels are too high, they can be harmful when amplified Audio levels are sporadic. Possibly very high output levels. FMECA Failure No. 3A Failure Mode Reset jumpers are shorted, thus created an effective “button pressed” state Criticality Remarks Microcontroller fails to run program, also cannot reprogram memory Micro not ATMEL is fried or I2C Nothing works on communicating with not configured one individual ARM9 properly for that channel channel Observation with Medium DMM Medium criticality because it disables the functionality of the system Observation with Medium Logic Analyzer Medium criticality because it disables the functionality of the channel 3C Erroneous/Sporadic information about audio levels is sent to ARM9 ATMEL is fried Audio levels are sporadic. Possibly very high output levels. Observation with High Logic Analyzer High criticality because if levels are too high, they can be harmful when amplified 3D PWM is only working on one channel PWM is disabled or fried Fader will only move automatically in one direction Observation with Low Oscilloscope Low criticality because it is simply a nuisance to the user. 3B Micro remains in reset mode Possible Causes Table 3 – ATMega32A Failure Effects Method of Detection FMECA Table 5 – Power Supply Failure Failure Mode No. 5A Excessive current draw, fuses continuously blown 5B Excessive current draw on regulator 5C Possible Causes Power rails shorted together Regulator is blown Rectifier circuit is Rectifier diodes or degraded and goes Capacitors are blown below dropout for regulator, causing a noisy voltage supply Failure Effects Method of Criticality Detection Observation High with DMM and continuity check Short causes a blown fuse, burnt out components, or even a fire Devices on a Observation particular power with DMM rail will not power on Preamp is noisy Observation with DMM Medium Remarks High criticality because if power traces are shorted, they can cause a fire Medium criticality because it disables the functionality of the unit Medium/Low Medium/Low criticality because it is a nuisance to the user, but also degrades the quality of the audio signal.